It must have taken a superhuman effort to pull together this massive production, the 19th in the Marvel Cinematic Universe, which features just about every character from all the movies thus far (except, sadly, San Francisco’s Ant-Man).

Though the result could have been an unwieldy, top-heavy, all-star mess (like 1963’s “It’s a Mad Mad Mad Mad World”), “Avengers: Infinity War” is a super movie — gigantic, but with an undeniable, powerful, humanity.

The movie’s plot has been teased in Marvel movies for years. Galactic bad guy Thanos (Josh Brolin) is attempting to collect six Infinity Stones; when he does, he can control everything, ending the universe.

It’s an old plot, but it has gravity. Like Killmonger in “Black Panther,” Thanos has his reasons, thinking his actions are for the good of all, even if they come with a vicious price.

As the movie goes on, the weight of Thanos’ task becomes heavier, and Brolin’s canny mo-cap performance makes the character almost touching.

It would be ludicrous to describe the events, except to warn that it’s more or less required to have seen last six movies in the franchise to get what’s going on.

Suffice to say, the screenplay by Christopher Markus and Stephen McFeely divides the pack of superheroes into smaller groups, which are more easily managed.

In the past, the Russos have been camera-shakers, and they still occasionally tend toward the too-quick cut, but they have improved. “Avengers: Infinity War” is their smoothest, best looking movie yet.

What’s different here is that there are consequences. Losses mean something, and it’s disquieting.

These characters have been onscreen for 10 years, since 2008’s “Iron Man,” and even longer on the comic page. Why do we care about them so much?

The answer could be twofold. Superheroes appeal to geeky, awkward kids because of the promise that underneath a misfit exterior lies a special power, if only others could see it.

In today’s troubled world, they also appeal to adults because they use powers to help others. It’s comforting to think that any of us would do the same, if we could.

While not perfect, superheroes are our best possible selves, freed and visualized.